title: A comparative study of affibody, panitumumab, and EGF for near-infrared fluorescence imaging of EGFR- and EGFRvIII-expressing tumors.
abstract: Aberrant overexpression and/or activation of epidermal growth factor receptor (EGFR) is associated with many types of cancers. EGFR variant III (EGFRvIII) is a common in-frame deletion mutant, which lacks a large part of the extracellular portion (exons 2-7), including components of the ligand-binding domain. Although EGFR has been extensively studied as a molecular imaging target, information about EGFRvIII-targeted molecular imaging is lacking. In this study, the EGFR-specific affibody, therapeutic antibody panitumumab, and ligand EGF were labeled with IRDye 800CW (Ex/Em: 774/789 nm), yielding Aff800, Pan800, and EGF800, respectively. The binding affinities of the labeled agents were compared in cell-based assays using a rat glioma cell line F98 parental (F98-p) lacking EGFR expression, and 2 F98-derived transgenic cell lines expressing EGFR or EGFRvIII (designated as F98-EGFR and F98-vIII, respectively). Results showed that all agents could bind to F98-EGFR, with Pan800 having the highest binding affinity, followed by Aff800 and EGF800. Pan800 and Aff800, but not EGF800, also bound to F98-vIII. In vivo animal imaging demonstrated that compared with F98-p tumors, F98-EGFR tumors generated higher signals with all three agents. However, in the case of F98-vIII, only Pan800 and Aff800 signals were higher. Analysis of tissue lysates showed that a large portion of Pan800 was degraded into small fragments in F98-EGFR and F98-vIII tumors, possibly due to proteolytic digestion after its specific binding and internalization. In conclusion, Pan800 and Aff800 could be used as imaging agents for both wild-type EGFR and EGFRvIII, whereas EGF800 only targets wild-type EGFR.
authors.affiliation: LI-COR Biosciences; Lincoln, NE USA.
authors.forename: Haibiao
authors.initials: H
authors.lastname: Gong
authors.affiliation: LI-COR Biosciences; Lincoln, NE USA.
authors.forename: Joy L
authors.initials: JL
authors.lastname: Kovar
authors.affiliation: LI-COR Biosciences; Lincoln, NE USA.
authors.forename: Lael
authors.initials: L
authors.lastname: Cheung
authors.affiliation: Division of Otolaryngology; Head and Neck Surgery; University of Alabama at Birmingham; Birmingham, AL USA.
authors.forename: Eben L
authors.initials: EL
authors.lastname: Rosenthal
authors.affiliation: LI-COR Biosciences; Lincoln, NE USA.
authors.forename: D Michael
authors.initials: DM
authors.lastname: Olive
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry*; D001557:Benzenesulfonates / Q000737:chemistry; D001667:Binding, Competitive; D045744:Cell Line, Tumor; D004815:Epidermal Growth Factor / Q000737:chemistry*; D066246:ErbB Receptors / Q000276:immunology / Q000378:metabolism*; D005456:Fluorescent Dyes; D064593:Heterografts; D006801:Humans; D007211:Indoles / Q000737:chemistry; D051379:Mice; D057054:Molecular Imaging; D061848:Optical Imaging; D000077544:Panitumumab; D051381:Rats; D011916:Rats, Inbred F344
chemical_list: D000911:Antibodies, Monoclonal; D001557:Benzenesulfonates; D005456:Fluorescent Dyes; C562366:IRDye 800CW; D007211:Indoles; C410723:epidermal growth factor receptor VIII; D004815:Epidermal Growth Factor; D000077544:Panitumumab; D066246:ErbB Receptors
keywords: epidermal growth factor receptor; fluorescence; in vivo imaging; near-infrared; tumor